Fatimah Hidayati

Friday, August 6, 2010

A scanning electron micrograph provides a color depiction of a small cancerous tumor within a human lung. The tumor is covered in microscopic hairlike structures called microvilli, which enable absorption and secretion. Smoking and other tobacco use are responsible for nearly all cases of lung cancer.

Cancer is a disease that begins as a renegade human cell over which the body has lost control. In order for the body and its organs to function properly, cell growth needs to be strictly regulated. Cancer cells, however, continue to divide and multiply at their own speed, forming abnormal lumps, or tumors. An estimated 6.7 million people currently die from cancer every year.

Not all cancers are natural-born killers. Some tumors are referred to as benign because they don't spread elsewhere in the body. But cells of malignant tumors do invade other tissues and will continue to spread if left untreated, often leading to secondary cancers.

Cancers can start in almost any body cell, due to damage or defects in genes involved in cell division. Mutations build up over time, which is why people tend to develop cancer later in life. What actually triggers these cell changes remains unclear, but diet, lifestyle, viral infections, exposure to radiation or harmful chemicals, and inherited genes are among factors thought to affect a person's risk of cancer.

Lung cancer is the world's most killing cancer. It claims about 1.2 million victims a year. Most of those victims are smokers, who inhale cancer-causing substances called carcinogens with every puff. Experts say around 90 percent of lung cancer cases are due to tobacco smoking.

Breast cancer now accounts for almost one in four cancers diagnosed in women. Studies suggest the genes you inherit can affect the chances of developing the illness. A woman with an affected mother or sister is about twice as likely to develop breast cancer as a woman with no family history of the disease. Lifestyle may also have an influence, particularly in Western countries where many women are having children later. Women who first give birth after the age of 30 are thought to have a three times greater risk of breast cancer than those who became mothers in their teens.

Geographical Distinctions

There are also stark geographic differences, with incidence rates varying by as much as thirtyfold between regions. In much of Asia and South and Central America, for example, cervix cancer is the most deadly in females. However, in North America and Europe another kind of gynecological cancer, ovarian cancer, is a more serious threat.

Among males, southern and eastern Africa record the second and third highest rates of oesophageal, or gullet, cancer after China, but western and central regions of Africa have the lowest incidence in the world. Differences in diet may explain this.

Nevertheless, the reasons why many cancers develop remain elusive. Brain cancer, leukemia (blood cancer), and lymphoma (cancer of the lymph glands) are among types that still mystify scientists.

Treatments

Yet ever more people are surviving diagnosis thanks to earlier detection, better screening, and improved treatments. The three main treatment options are surgery, radiotherapy and chemotherapy. Radiotherapy, also called radiation therapy, involves blasting tumors with high-energy x-rays to shrink them and destroy cancerous cells. Chemotherapy employs cancer-killing drugs.

Even so, future cancer cases are predicted to climb, since the world's population is aging. The proportion of people over age 60 is expected to more than double by 2050, rising from 10 percent to 22 percent. This will add an estimated 4.7 million to the cancer death toll by 2030.

Radiation Treatment

Photograph by Karen Kasmauski

For Bonnie Frost, radiation offers hope in her fight against cancer. At the University of California's Lawrence Berkeley Laboratory, doctors pinpoint the tumor pressing against her spinal cord with a CT scanner, then treat it with heavy-ion radiation. The mask and brace keep her head perfectly still.

Lymphoma accounts for one in ten childhood cancers, affecting up to three children per 100,000. Non-Hodgkin's is slightly more common than Hodgkin's, but both types are very rare in children under three years. Boys are affected slightly more often than girls.

As recently as 1950, lymphoma was almost always fatal, but these days up to 95 per cent of those newly diagnosed with Hodgkin's lymphoma can expect to be cured. NHL is less easily treated: about 77 per cent of children are still alive five years after diagnosis.

Lymphatic system

The lymphatic system is made up of thin tubes called lymph vessels that run throughout the body, often alongside blood vessels. These vessels carry lymph, a colourless, watery fluid that contains white blood cells called lymphocytes.

Dotted along the network of lymph vessels are groups of small, bean-shaped lumps called lymph nodes or glands. Clusters of lymph nodes are found under your arms, around your neck and under your chin, and throughout the pelvis, groin, abdomen and chest.

The nodes make and store infection-fighting cells, especially lymphocytes. It's these lymphocytes that become cancer cells in lymphoma.

Lymphoma can start in almost any part of the lymphatic system, then spread to almost any other part of the body including the liver, bone marrow (the spongy tissue inside the large bones of the body that makes blood cells) and the spleen (an organ in the upper abdomen that makes lymphocytes and filters old blood cells from the blood).

Common symptoms

·painless swelling of the lymph nodes

·fever for which no cause can be found

·fatigue or extreme tiredness

·paleness

·night sweats (usually a sign of Hodgkin's)

·weight loss

Often, lymphoma spreads throughout the body before a person is aware that they have a problem.

Causes

The exact cause of lymphoma isn't yet known, but there's an inherited tendency and brothers or sisters of a child with lymphoma are slightly more likely than average to get it too.

But this genetic tendency alone isn't enough to trigger the disease - there have to be other aggravating factors. It's suspected that infection with viruses and bacteria can predispose to lymphoma.

People with HIV or Epstein-Barr virus, or those taking immunosuppressive drugs (such as patients who've had kidney or lung transplants) are at greater risk of getting some types of lymphoma. About 30 per cent of all AIDS patients contract it, for example. Alternatively, there may be an environmental factor, such as exposure to pesticides.

It's important to get an exact diagnosis. Slightly different types of white blood cell are involved in Hodgkin's and non-Hodgkin's lymphoma, and the exact type of cancer is determined mainly by what the cells look like under a microscope.

It's important for doctors to find out exactly which type of lymphoma is involved as they need slightly different treatments and have different prognoses or cure rates.

Doctors will also 'stage' the cancer - this means working out how far it has spread around the body.

Treatment

Lymphomas are usually treated with a combination of chemotherapy, radiation, surgery and bone-marrow transplants. The cure rate varies greatly depending on the type of lymphoma and the progression of the disease, as well as how healthy the child is generally.

·Chemotherapy drugs are used to kill cancer cells and shrink tumours.

·Radiotherapy involves the use of high-energy x-rays to kill the cancer cells.

·Bone marrow transplantation is a newer type of treatment, which allows very high doses of anti-cancer drugs to be given.

Many children with lymphoma will be offered the chance to be treated as part of a clinical trial. While they or their families may be frightened by the idea that they're being used as some sort of guinea pig, they should be very carefully monitored by doctors during the trial. Trials are the only way to find better treatments.

Scientists have developed a new way to target viruses which could increase the effectiveness of antiviral drugs. Instead of attacking the virus itself, the method developed at Edinburgh University alters the conditions which viruses need to survive and multiply.

By making the site of infection less hospitable, the virus becomes less able to mutate and build up resistance to drugs. The experts were also able to target more than one virus at the same time.

Viruses take up residence in host cells within the body, which produce proteins that enable the virus to multiply and survive.

A problem with current antiviral therapies, which generally target the virus, is that viruses can mutate to become resistant”

- Dr Amy Buck University of Edinburgh

The study, published in the journal Proceedings of the National Academy of Sciences, analysed molecules known as micro-RNAs, which regulate how much of these proteins are made. The scientists were able to manipulate the micro-RNA levels, which enabled them to control a network of proteins and stop viruses from growing.

Most existing antiviral therapies only work against one virus. However, by adapting the virus host environment the researchers were able to target different types of viruses. It is hoped that the research could lead to new treatments for patients suffering from a range of infections.

Dr Amy Buck, of the university's centre for immunity, infection and evolution, said: "A problem with current antiviral therapies, which generally target the virus, is that viruses can mutate to become resistant. "Since new viral strains emerge frequently, and many infections are difficult to diagnose and treat, it is important to find new ways of targeting infection.

"Our hope is that we will be able to use host-directed therapies to supplement the natural immune response and disable viruses by taking away what they need to survive. "Scientists studied the herpes family of viruses, which can also cause cancer. They also looked at the Epstein-Barr virus, and the Semliki Forest virus, which is mainly spread by mosquitoes.

Both viruses have different characteristics. Viruses from the herpes family replicate inside the nuclei of cells, while the Semliki Forest multiplies outside the nucleus of a cell. The study was funded by the Wellcome Trust and the Biotechnology and Biological Sciences Research Council.

An implant placed under the skin can instruct the immune system to attack and kill cancer cells, at least in mice, say researchers. It is the first "cancer vaccine" delivered in the form of a plastic implant that can destroy tumours, say the Harvard University team. It works by attracting certain immune cells and showing them what the tumour in question looks like.

Cancer Research UK said that vaccine research was showing "real promise". Cancer cells are good at evading the immune system because the body does not recognise them as "foreign".

Plastic disc

The idea of a vaccine to create an immune attack against a tumour is not a new one and there are versions currently in clinical trials. But most other studies have looked at removing immune cells from the body, reprogramming them to recognise the individual's cancer and then returning them.

This study provides some useful insights into how we can effectively train the immune system to recognise and destroy cancer cells

- Dr Joanna Owens, Cancer Research UK

In the latest study, researchers developed an 8mm plastic disc that releases chemicals that attract a specific type of immune cell called a dendritic cell. Immune cells can access the disc, which is implanted just under the skin. Once inside, they are exposed to proteins found on the surface of the cancer cells to be targeted.

With this information, the dendritic cells move on to the lymph nodes where they tell another type of immune cell, known as T cells, to hunt down and kill the cancer cells. In mice with skin cancer, the implant was shown to successfully eliminate the tumours, the journal Science Translational Medicine reported.

Healthy tissue

The researchers believe such implants could one day be used alongside chemotherapy and surgery to treat cancer. In theory, the fact the immune system only targets the specific cancer cells avoids causing damage to healthy tissue and it is hoped the technique might produce long-term resistance reducing the chance of relapse.

For use in humans, the structure of the implant itself would need little modification but researchers said the immune activation components would need to be altered. Study leader Professor David Mooney, an expert in bioengineering, said the technique was a "major step forward" in cancer vaccine design.

"Inserted anywhere under the skin - much like the implantable contraceptives that can be placed in a woman's arm - the implants activate an immune response that destroys tumour cells," he said.

Dr Joanna Owens, science information manager at Cancer Research UK, said research into therapeutic cancer vaccines was beginning to show "real promise". "This study provides some useful insights into how we can effectively train the immune system to recognise and destroy cancer cells.

"The use of an implant to deliver the vaccine is particularly interesting and the results look encouraging but more research is needed to see if the technology can be scaled up and adapted for use in people."

Doctors say they have used a genetically engineered herpes virus to treat successfully patients with head and neck cancer. A London hospital trial of 17 patients found that use of the virus alongside chemotherapy and radiotherapy helped kill the tumours in most patients. It works by getting into cancer cells, killing them from the inside, and also boosting the patient's immune system.

Further trials are planned for later in the year. Head and neck cancer, which includes cancer of the mouth, tongue and throat, affects up to 8,000 people every year in the UK. Study leader Dr Kevin Harrington, who is based at the Institute of Cancer Research in London, said current treatments were effective if the cancer was picked up early but that many patients were not diagnosed until it was more advanced.

The herpes virus, which is also being tested in patients with skin cancer, is genetically manipulated so that it grows inside tumour cells but cannot infect normal healthy cells. Once there it has a triple effect - it multiplies, killing tumour cells as it does so, it is engineered to produce a human protein that activates the immune system and it also makes a viral protein that acts as a red flag to immune cells.

'Potential weapon'

In the 17 patients injected with the virus, in addition to their standard treatment, at the Royal Marsden Hospital, 93% showed no trace of cancer after their tumour had been surgically removed. More than two years later, 82% of patients had not succumbed to the disease. Only two of 13 patients given the virus treatment at a high dose relapsed, the journal Clinical Cancer Research reported.

There were no safety concerns with use of the virus, the researchers said, and it is hoped the virus could one day be used to fight other types of cancer. "Around 35 to 55% of patients given the standard chemotherapy and radiotherapy treatment typically relapse within two years, so these results compare very favourably," said Dr Harrington.

He is now planning a trial comparing the viral treatment with the standard treatment in people newly diagnosed with head and neck cancer. Dr Alison Ross, senior science information officer at Cancer Research UK, said it would be some time before the treatment could be used in patients as it still needed to be tested directly against standard treatment.

But she added: "This small study highlights the potential of using genetically modified viruses as a weapon to fight cancer."